What Are Calories—And Why Are They so Important?


 What Are CaloriesYou watch for them on food labels, you mind your intake, but how much do you really know about calories—besides the fact that most diets have a little too much of them? Now is as good a time as any to indulge your curiosity, so let’s take a look at what a calorie is—and isn’t.

First off, a calorie is not a nutrient. It is not something physical. You cannot put a cracker under an electron microscope and point out the calorie particles, for instance. A calorie is a unit of energy. Specifically, it is the amount of heat required, under normal atmospheric conditions, to raise the temperature of one gram of water one degree Celsius. Calories actually come in two units of measurement. The first is the “small calorie” (cal.) which is the one defined above. The second is the “large calorie” (Cal. or kcal) which is the energy needed to raise one kilogram of water by one degree Celsius. When you read the calorie information on food packaging, you are reading it in large calories.

How Are Calories Measured?

Picture a sealed container filled with a set amount of cold water. Inside this container is another container filled with oxygen and the (dehydrated) food item you want to learn the caloric energy of. A spark is used to ignite the oxygen and set fire to the food inside the second contained. As the food burns, scientists track how much the water temperature changes and some number crunching afterwards provides the caloric energy of the food.

This device is called a “bomb calorimeter” but it isn’t used as much nowadays. Instead, manufacturers often calculate the calories of their products by adding up the calories produced by its nutrients and ingredients. This is easier than using the calorimeter each time, since the nutrient amounts are already known and their caloric value doesn’t change.

Where Calories Get Messy

Up to now, calories may appear more-or-less a matter of straightforward math. However, things get trickier when it comes to how calories impact your weight. Basically, excess energy gets stored in fat by your body for use later so eating more calories than you use leads to weight gain. This is not a straightforward process. Metabolism varies from person to person and with age, meaning how well you can handle calories is going to be different from those around you and there are additional concerns about how your body processes caloric energy.

First, not all nutrients in your food are used the same way. Fiber, for instance, is not digestible so its calories never get used—and not all manufacturers subtract it from their counts. Other nutrients are used more efficiently than others, such as how the calories in vitamins get burned faster than those in fats. When people speak about “empty calories”, what they are referring to are calories that don’t have as much nutritional value—usually from added fats, sugars, or carbs. These are more likely to be retained by the body, causing a greater contribution to weight. This does not mean that you have to avoid all extra fats, sugars, or carbs, merely that you should be mindful of where the calories in your food are coming from and how the labeling works. When looking at a food label that is, for example, high in fiber but low in fat, the calorie count may be far larger than your body would ever receive.

Bottom Line

  • Calories are a unit of energy obtained from the substances in food.
  • Your body handles calories differently depending on what nutrient it is packaged in.
  • Personal metabolism affects how much of the calories in your food gets process and how quickly.
  • When looking at food nutrition labels, a high calorie count isn’t automatically a deal-breaker so long as the item is low in fats, carbs, and sugars.
  • You can set fire to your dinner so long as you say it’s for science.

Sources for Today’s Article:
Falin, L., “How Are Calories in Food Measured?” Quick and Dirty Tips web site, October 17, 2014; http://www.quickanddirtytips.com/education/science/how-are-calories-in-food-measured?page=1, last accessed March 1, 2016.
Nordqvist, C., “Calories: Fast Food and Empty Calories,” Medical News Today web site, February 15, 2016; http://www.medicalnewstoday.com/articles/263028.php?page=2.
“How Do Food Manufacturers Calculate the Calorie Count of Packaged Foods?” Scientific American web site, July 31, 2006; http://www.scientificamerican.com/article/how-do-food-manufacturers/, last accessed March 1, 2016.